Investigating the molecular basis of the serological Rh D-negative phenotype in Indonesia: nature, frequency, and impact for diagnostics.

BACKGROUND

Although widely studied and reported for more than 30 years, the molecular basis of Rh D-negativity has remained unexplored in several regions of the world, including in Indonesia, Southeast Asia.

STUDY DESIGN AND

METHODS

A subset of 436 Indonesian blood donors originally typed D-negative (D-) by routine serological testing was analyzed at the molecular level by a previously reported three-step strategy, including 1/quantitative multiplex PCR of short fluorescent fragments (QMPSF); 2/Sanger sequencing of RHD exon 9; and 3/ Sanger sequencing of all RHD exons, allowing the identification of structural variants, the c.1227G>A single nucleotide variant (SNV) defining the Asian type DEL allele (i.e., RHD*01EL.01), and all other SNVs, respectively.

RESULTS

Deletion of the whole RHD gene (RHD*01N.01) is by far the most common allele (allele frequency = 0.8245), followed by RHD*01EL.01 (0.0849), RHD*01EL.44 (0.0241) and RHD*01N.03 (0.0172). In the 18 others, five alleles were novel, including RHD*1220delT that is assumed to result in a premature stop codon; RHD*c.635-1A and a complex hybrid allele carrying the c.486+5A variant, both of which disrupting splicing; and a complex RHD*01N(ex8del) allele deleting a ~2 kilobase genomic region including exon 8.

CONCLUSION

Overall, we report for the first time the molecular basis of D- phenotype in the Indonesian population. Although characterized by some specificities as illustrated by the novel variant alleles, it seems that the distribution of the variant alleles globally mimics what is observed in another Southeast Asian country, that is Thailand, thus allowing implementation of common guidelines at a transnational level.